Field of the Invention
The present invention relates to a communication apparatus for communicating with a relaying device in a network.
Description of the Related Art
A network interface card (NIC) has conventionally been used for enabling a digital multi-function peripheral that performs printing, transmission, and the like to communicate with other devices via a network such as a local area network (LAN).
Ethernet is popular as a representative network standard. A NIC compliant with the Ethernet standard can perform communication by selecting one of communication speeds of 10 Mbps, 100 Mbps, and 1000 Mbps.
Recently, power saving has been required of the digital multi-function peripherals. In this regard, for example, Japanese Laid-Open Patent Application No. 2001-154763 discusses a technique for saving power by reducing a communication speed of an NIC when the digital multi-function peripheral operates in a power-saving mode.
To achieve more power saving, in addition to the reduction in the communication speed as discussed in Japanese Laid-Open Patent Application No. 2001-154763, Japanese Laid-Open Patent Application No. 2007-276341 discusses a technique for cutting off power supply to a part of a communication apparatus when the communication apparatus operates in a power-saving mode.
As a recent network related technique, virtual local area network (VLAN) has been popular. The VLAN technique virtually divides a plurality of physically connected computer terminals on a network into a plurality of groups (“virtual networks”) by using a relaying device such as a switching hub to manage the groups as if they belong to different LANs respectively. The VLAN technique is further classified into a static VLAN technique and a dynamic VLAN technique. In the static VLAN technique, computer terminals are divided into a plurality of groups for each port of a switching hub. In the dynamic VLAN technique, a switching hub virtually divides a plurality of computer terminals into a plurality of groups to manage the terminals based on information (for example, media access control or MAC address) acquired from each computer terminal connected to a port.
It is assumed that a communication link with a switching hub is cut off (“linked-down”) in a communication apparatus connected to the switching hub compliant with the dynamic VLAN technique. In such a case, to reconnect (“link-up”) the communication link with the switching hub, the communication apparatus has to retransmit information such as a MAC address to the switching hub. This is because the switching hub supporting the dynamic VLAN technique considers that the computer terminal whose communication link has been cut off no longer belongs to (“participates in”) the VLAN by cutting-off of the communication link. To participate in the VLAN including the switching hub, as discussed in Japanese Laid-Open Patent Application No. 2009-278240, the communication apparatus has to transmit information such as a MAC address to the switching hub.